Influence of Pre-injection Control Parameters on Main-injection Fuel Quantity for an Electronically Controlled Double-valve Fuel Injection System of Diesel Engine

A simulation model of an electronically controlled two solenoid valve fuel injection system for a diesel engine is established in the AMESim environment.The accuracy of the model is validated through comparison with experimental data.The influence of pre-injection control parameters on main-injection quantity under different control modes is analyzed.In the spill control valve mode,main-injection fuel quantity decreases gradually and then reaches a stable level because of the increase in multi-injection dwell time.In the needle control valve mode,main-injection fuel quantity increases with rising multi-injection dwell time;this effect becomes more obvious at high-speed revolutions and large main-injection pulse widths.Pre-injection pulse width has no obvious influence on main-injection quantity under the two control modes;the variation in main-injection quantity is in the range of 1 mm3.

Measurement and analysis of cycle fuel injection quantity for electronic unit pump

The cycle fuel injection quantity is accurately measured for electronic unit pump （EUP） operating at high, middle and low speeds by using displacement method based on EFS instantaneous mono-injector qualifier. On the basis of the experi- mental data about fuel injection quantity and fuel pressure, the variation of inconsistency in fuel injection quantity of EUP and the influence factors in different operating conditions are concluded. The results show that the inconsistency is lowest in maximum torque condition, while on the start and maximum power conditions, it is higher.

Teaching Reform of Courses for Ideological and Political Education Based on Simulation Information Technology:Taking the Course Group of Engineering Valuation in Jiangxi Normal University for Example

In higher engineering education,professional courses and ideological and political theory courses go in the same direction,which is an important task of the current professional curriculum construction.This paper introduces the key and difficult problems in the teaching content of the course Engineering Valuation in the Department of Engineering Management and Real Estate of Jiangxi Normal University.Based on the characteristics of simulation information technology such as BIM and VR and the differences of ideological and political elements,it updates and improves the cases of courses for ideological and political education,gives full play to the synergistic effect,and realizes the"triple"talent training goal of knowledge,ability and literacy.

Application of Artificial Neural Network in Engineering

This paper mainly studies the dynamic direction of engineering valuation based on the artificial neural network methods,and seeks for a set of rapid,convenient and practical valuation models,for building construction projects.

Research Progress on Evaluation Frameworks of Regional Ecological Sustainability

As natural ecosystems provide the material basis and fundamental support for regional sustainable devel-opment,the sustainability of natural ecosystems is an important prerequisite and a viable approach for the achievement of regional sustainable development.It is also the final criteria to assess whether sustainable development paradigm is successful.Along with the increasing impacts of human activities on natural ecosystems,the evaluation of regional ecological sustainability has become one of the key issues for research on macro ecology and sustainable development.Based on different unit of indicators,this study firstly groups the evaluation frameworks of regional ecological sus-tainability into three major types:comprehensive index evaluation with dimensionless unit,monetary valuation,and biophysical quantity measurement.We then discuss and compare these types in terms of basic principles,scope of ap-plications,advantages and shortcomings.Finally,drawn on the discussion about characteristics of ecological sustain-ability,we outline the current trend and future directions of regional ecological sustainability evaluation,for instance,transition from sustainable development evaluation to sustainability science,integration of goal-oriented and problem-solving approaches,combination of spatial pattern analysis and ecological sustainability evaluation,and en-hancement of ecological sustainability evaluation at landscape scale.

A Bayesian Network Approach for Offshore Risk Analysis Through Linguistic Variables

This paper presents a new approach for offshore risk analysis that is capable of dealing with linguistic probabilities in Bayesian networks （ BNs）. In this paper, linguistic probabilities are used to describe occurrence likelihood of hazardous events that may cause possible accidents in offshore operations. In order to use fuzzy information, an f-weighted valuation function is proposed to transform linguistic judgements into crisp probability distributions which can be easily put into a BN to model causal relationships among risk factors. The use of linguistic variables makes it easier for human experts to express their knowledge, and the transformation of linguistic judgements into crisp probabilities can significantly save the cost of computation, modifying and maintaining a BN model. The flexibility of the method allows for multiple forms of information to be used to quantify model relationships, including formally assessed expert opinion when quantitative data are lacking, or when only qualitative or vague statements can be made. The model is a modular representation of uncertain knowledge caused due to randomness, vagueness and ignorance. This makes the risk analysis of offshore engineering systems more functional and easier in many assessment contexts. Specifically, the proposed f-weighted valuation function takes into account not only the dominating values, but also the a-level values that are ignored by conventional valuation methods. A case study of the collision risk between a Floating Production, Storage and Off-loading （FPSO） unit and the anthorised vessels due to human elements during operation is used to illustrate the application of the proposed model.

The most economic cavity quantity in injection mould CAD based on concurrent engineering

Presents the conception of concurrent engineering employed for CAD/CAM of injection moulds by closely combining the management science with the manufacturing techniques with the cost of processing, material cost, etc taken into consideration from the conceptural design to delivery of products and concludes with the results of analyses that the cost of finished plastic parts is lower, the production efficiency is higher while energy is saved.

临界温度下循环喷油量对柴油机冷起动和排放特性的影响

为探明循环喷油量对小型农用柴油机冷起动特性和排放性能的影响规律,同时寻求其临界温度下的最佳循环喷油量,该研究以一款直列双缸高压共轨柴油发动机为研究对象,利用环境模拟舱整机试验平台,通过多次预试验测得海拔2000 m下,该机不开启预热装置能够成功起动的临界温度为-5℃。在此工况下,采用3次喷射方式,通过改变主喷油量研究循环喷油量对该机冷起动特性和排放性能的影响。结果表明:较大或较小的循环喷油量均会导致柴油机冷起动时间增加,甚至起动失败;随着循环喷油量增大,冷起动时间先减小后增加,循环喷油量为20 mg时冷起动时间最短,且HC、CO排放峰值均最低,分别为12984和3008 mg/L;增大或减少循环喷油量均会导致HC和CO排放峰值增加。循环喷油量较大时,CO排放峰值显著增加,并且峰值出现时刻提前。改变循环喷油量对NOx排放峰值有较大影响,循环喷油量为30 mg时NOx排放峰值最小,为368 mg/L。综合考虑,海拔高度2000 m,环境温度-5℃工况下该柴油机起动的最佳循环喷油量为20 mg。研究结果可为柴油机冷起动特性和排放优化提供支撑。

基于工程经济性的公路悬索桥主缆最优垂跨比研究

为寻求工程经济性最优的公路悬索桥主缆垂跨比,以我国近年多座采用混凝土桥塔的单跨公路悬索桥为背景,建立主缆、锚碇、桥塔基础工程量的直接函数模型和桥塔塔身工程量的非线性函数拟合模型,对跨度750~2250 m、单层车道数4~8及双层车道数6+4、垂跨比1/14~1/6共952种布置形式的悬索桥进行大范围关于主缆垂跨比的工程经济性研究,并以2座实桥为算例分析主缆垂跨比对悬索桥静、动力性能及抗风性能的影响。结果表明:主缆垂跨比对悬索桥工程经济性影响显著;悬索桥主缆最优垂跨比与跨度相关,而车道数、加劲梁荷载集度的影响相对较小,涉水和不涉水的差异也不显著;基于工程经济性考虑,跨度750~2250 m的悬索桥主缆最优垂跨比为1/6.5~1/8.5,比经验值增大较多。2座实桥算例分析表明随着垂跨比增加,加劲梁挠度和活载应力有所增加,抗风性能略有提升,建议方案设计阶段加大垂跨比研究范围、对工程经济性和桥梁力学性能进行综合比选。

引燃柴油量对双燃料发动机循环变动的影响

为了降低重型高压共轨柴油机燃用LNG-柴油的燃烧循环变动,优化引燃柴油量控制,通过双燃料发动机试验台架,研究了在最大转矩转速1600r/min,功率输出为73kW工况下,随引燃柴油喷油量的增加,峰值压力、峰值压力升高率、平均指示压力循环变动的变化趋势。研究结果表明,随引燃柴油量的增加,双燃料发动机的峰值压力、峰值压力升高率和平均指示压力的循环变动趋势相同,它们的均值均增大,标准差减小,循环分布集中,循环变动系数降低。在不导致爆震燃烧的前提下,适当增大引燃柴油量,能够改善双燃料发动机的燃烧稳定性。

燃油温度对柴油液相喷雾特性的影响

在低温环境下柴油黏度增大流动性变差,抑制了柴油机柴油喷雾的雾化和蒸发,直接影响柴油机的冷启动可靠性。为解决上述问题,采用背光法试验对比研究高温、低温柴油在不同工况条件下喷雾宏观结构的变化规律,并利用MATLAB对拍摄的喷雾图像进行数字图像处理获取喷雾宏观特性参数。试验结果表明,喷孔直径0.12 mm时,随着喷油压力的变化柴油温度对喷油量的影响比较明显,黏性力的持续作用减慢了靠近壁面的流体层的流动速度,抑制柴油喷出,柴油温度低于0℃时随着柴油温度降低喷油量减少,高压时柴油温度降低导致液滴间增强的黏性力在动能和惯性力的作用下反而促进柴油持续喷出,喷油量随着柴油温度降低而增多。喷油压力为75 MPa时,柴油温度降至-20℃相较38℃柴油喷油量增加了近23.87%。并且小孔径下柴油温度降低液滴间黏性力增大,导致喷雾液滴尺寸增大,液滴所具有的动量越大,削弱柴油喷雾径向发展趋势,轴向运动能力增强,随着柴油温度的降低,喷雾贯穿距增大而喷雾锥角减小,柴油温度从38℃降至-20℃,柴油喷雾在0.70 ms时刻喷雾贯穿距增大了39.89 mm。喷孔直径为0.28 mm时,喷射压力小于75 MPa,喷油量随着柴油温度的降低而减少,相同喷油压力下柴油更多的动量消耗于克服更大的内部摩擦力,使其到达最远距离的能力减弱,降低柴油温度会导致喷雾贯穿距和喷雾锥角均减小,当喷油压力为75 MPa时,0.70 ms时刻-20℃柴油喷雾贯穿距相对38℃柴油喷雾贯穿距缩短了30.86 mm。相同喷射压力下增大喷孔直径,-20℃柴油喷雾贯穿距减小,喷雾锥角增大。随着喷油压力的提升柴油温度对喷雾宏观特性的影响更加突出,喷油压力越高降低柴油温度造成的喷雾贯穿距缩短趋势越明显。研究结果可为柴油机冷起动过程低温柴油喷雾特性提供支撑。

基于赛课融通的新工科专业课程建设研究——以“工程量清单计价”课程为例

高校在新工科专业课程建设框架下开展赛课融通模式探索,对于促进理论教学与实践教学结合、激发大学生学习积极性、提升大学生职业适应能力、开辟新工科人才培养新路径等具有重要意义。“工程量清单计价”课程应当在明确赛课融通模式建设主体内容的基础上,从打造特色化赛项品牌、拓展赛项成绩应用、多元化开展合作、建立健全评价考核体系等角度入手,持续推动教学模式的优化与完善。

建筑工程计量与计价课程思政AEE模式探究

建筑工程计量与计价课程是建筑工程技术专业必修的主干专业理论课程,如何在课程教学中进行思政教育,既是当前建筑专业教师面临课程改革的一个重要任务,也是实现全方位全方面全过程推进建筑专业青年大学生思想政治工作的有效路径。在对建筑工程计量与计价课程思政的重要意义和目前存在的主要问题进行了分析的基础上,创造性和针对性地提出了建筑工程计量与计价课程思政的AEE模式,并以其中的思政元素挖掘、思政课程设计两个阶段为研究重点,提出了以启发式融入、讨论式发散、案例式体验和任务式驱动组成的AEE模式的实践路径。

基于逐级映射的铁路工程自动验工计价方法研究

针对铁路工程验工计价业务模式存在的依赖业务人员能力、效率低下、数据难共享、机制不透明等问题,提出一种基于逐级映射的铁路工程自动验工计价方法,即通过WBS、EBS、Qlist数据进行层级编码并添加节点层级,形成验工计价数据模板;同时建立各数据模板间的基础映射关系,支持用检验批结果驱动基础映射关系自动归集验工计价数量;经过线上业务协同流程,可以实现一键式验工计价。在实际铁路建设项目中应用后,方法的可行性、可靠性、简易性得到验证,提升业务效率,计价过程支持追溯,提升了计价工作透光度。

农牧交错区生态工程建设对生态系统服务的影响

查明农牧交错区生态工程建设对区域生态系统服务的影响可为生态环境建设和优化管理提供有益参考。该研究以农牧交错区典型县域张北县为例,综合利用光谱混合分解模型、InVEST模型和回归分析方法,基于原始影像的端元分解、土地利用/覆被制图和生态系统服务评估,从生态用地数量和质量变化两个角度探析生态工程建设对区域生态系统服务的影响。结果表明:1)2000—2020年间,生态工程建设影响下张北县林地分布范围迅速扩张,耕地和草地面积持续收缩,林地扩张与耕地和草地缩减存在一定的空间重合现象。张北县土壤保持、水源涵养和防风固沙3种服务整体表现为强化趋势,但具体分布存在明显的空间异质性;2)在生态用地数量变化方面,生态用地总面积不断增长,20 a间增加了687.67 km^(2)。其中,林地面积、草地面积及其总面积增加对土壤保持和水源涵养服务的提升效果明显,而仅有林地面积增加对防风固沙服务具有积极作用。在生态用地质量变化方面,20 a间林地端元要素丰度值平均含量下降了0.108,其质量整体呈衰退趋势。20 a间草地端元要素丰度值平均含量增加了0.099,其质量整体表现为微弱上升的态势。林地和草地质量改善均增强了土壤保持、水源涵养和防风固沙服务,但防风固沙服务对林地和草地质量变化最为敏感。研究结果为生态工程建设对生态系统服务的影响研究提供了新的认知视角,未来应从生态用地精细分类对生态系统服务的影响差异方面深化研究,也应重视气候要素对区域生态系统服务的相对贡献。

无资料地区闸站调度下江湖水量交互规律研究

为解决无资料地区通江湖泊水量交互规律,以涨渡湖为例,将江湖水量交互原理同遥感解译理论相耦合,提出一种无资料地区闸站调度下江湖水量交互规律研究方法,基于Google Earth Engine(GEE)平台分析湖泊面积变化,结合同期降水、蒸发和湖泊特性,计算江湖交互水量。结果表明,湖泊多年月平均面积总体变化趋势一致,呈规律性变化,2~6月呈下降趋势,7~11月呈上升趋势,变化范围在40~47 km^(2)之间;每年2~6、11~12月湖水入江,7~10月、12月~次年1月江水倒灌入湖。结果可为其他无资料地区闸站调度下江湖水量交互规律研究提供参考。

预喷与外部EGR对车用柴油机燃烧和排放的影响

以某四缸水冷车用柴油机为样机,应用GT-Power软件搭建车用柴油机仿真模型,通过改变预主喷间隔、预喷油量和废气再循环(EGR)开度,研究中等负荷及转速工况下,不同的预喷策略以及引入外部EGR后两者共同作用对车用柴油机燃烧和排放性能的影响。试验结果表明:随着预喷正时从-17°CA提前到-37°CA,预喷油量从3.3 mg增加到9.9 mg,燃烧特性、碳氢化合物(HC)和一氧化碳(CO)排放均得到有效改善,但燃油消耗率和NOx排放总体呈上升趋势。在预喷策略的基础上引入外部EGR后,随着EGR率从5%增加到25%,NOx排放保持在较低水平,但缸内燃烧变差,HC和CO排放增多。在1 800 r/min、50%负荷的试验工况下,较小的预喷油量、中等的预喷间隔以及中等的EGR开度更有利于车用柴油机的燃烧和排放。

双升程电控喷油器多次喷射油量波动特性研究

为实现船用柴油机高压共轨系统喷射的柔性和稳定控制,提出一种双升程电控喷油器,基于搭建的喷油器AMESim仿真模型,探究了喷油器不同多次喷射模式下的油量波动特性.结果表明:大升程预喷模式下的主喷量标准差随预喷量的增加先上升后下降,而小升程预喷模式下的主喷量标准差随预喷量呈幅值逐渐降低的波动变化趋势.总体上,在预喷量为161~660 mm^(3)范围,小升程预喷模式在降低主喷量波动程度方面比大升程预喷模式更占优势.预喷射采用小升程喷射模式且预喷量一定时,升程切换延迟为0.2 ms的靴形主喷模式在降低主喷量波动程度方面略优于相同主喷脉宽或相同单次喷射油量的大升程主喷模式.大升程和小升程后喷模式下的后喷量标准差随主喷脉宽和目标后喷量均呈波动变化趋势,且小升程后喷模式下的后喷量标准差波动程度更小.与大升程后喷模式相比,小升程后喷模式在降低后喷量波动程度方面更占优势.

基于清单计算规则的BIM建模设计与算量计算方法研究

本文根据工程量清单规范要求,分析了利用REVIT软件建模设计导出实体工程量与清单工程量的偏差影响因素,在此基础上提出了符合工程量计算规则的BIM建模设计规则和计算方法。将BIM模型用于造价和成本管理,已经成为工程信息化管理的核心需求。以BIM技术为基础,提高项目管理能力、保证深化设计的质量以及实现建筑施工项目标准化、精细化的要求。按照工程量计价规则建立有效的建模设计规范和设计流程,结合明细表统计规则的修正,可以很好地解决建筑结构工程的建模设计与工程量统计问题,可很好地满足工程应用要求。

基于小波分解-LSTM的航空发动机润滑油量模型

为了描述航空发动机润滑油量在飞机飞行中的变化,综合小波分解和长短期记忆网络(LSTM)的优点构建了小波分解-LSTM模型,模型的输入是由发动机高压转子转速、低压转子转速、飞机飞行高度、飞行姿态等参数构成的多组时间序列,输出为对应的润滑油量序列。采用实际运营中的快速存储记录器(QAR)数据,选取润滑油量波动较大的飞机飞行下降阶段进行建模。对润滑油量数据进行温度校准,去除热胀冷缩因素的影响;选择影响润滑油量变化的关键因素,包括高压转子转速、飞机姿态、飞行高度、飞行速度等11个输入因素;对这些输入因素和经温度校准后的润滑油量数据做小波分解,降低数据中噪声的影响并减小数据量,以加快后续机器学习模型的训练速度;采用LSTM神经网络训练数据模型,根据输入因素计算出润滑油量数据。结果表明:基于真实飞行数据测试结果显示,以升为单位,模型计算的润滑油量与实际润滑油量间均方误差约为0.1,说明模型能够有效描述飞机下降阶段中润滑油量的变化,可用于发动机滑油系统健康监控,为发动机滑油系统预测性维护提供新的方法支持。